The present invention relates to disc drive data storage systems and, more particularly, to a disc head slider for carrying a read/write transducer within a disc drive.
Disc drives are well known in the industry. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to lift and fly above or in close proximity to the disc surface.
One type of slider is a xe2x80x9cself-loadingxe2x80x9d air bearing slider, which includes a leading taper (or stepped-taper), a pair of raised side rails, a cavity dam and a subambient pressure cavity. The leading taper is typically lapped or etched onto the end of the slider that is opposite to the recording head. The leading taper pressurizes the air as the air is dragged under the slider by the disc surface. The cavity dam provides an expansion path for the air to de-pressurize as it is dragged into the sub-ambient pressure cavity by the disc velocity. The expanded air in the cavity provides a self-loading force which forces the slider toward the disc surface. The counteraction between positive pressure developed along the side rails, the preload force provided by the suspension and the self-loading force provides the air bearing with a high vertical stiffness.
The physical separation between the slider and the disc surface at the recording head is an important parameter to disc drive performance. It is desired to minimize variation in the head clearance or xe2x80x9cfly heightxe2x80x9d in response to various modes of vibration in the disc drive.
Rather than using the entire rail surface as a bearing surface, future slider designs may utilize many small bearing pads positioned on the rail surfaces which together form the overall bearing surface. These small bearing pads present surface contour changes along the rails which create pressure gradients over the small pad areas. It has been found that these pressure gradients can enhance vibration damping capabilities of the slider. In order to achieve high stiffness in addition to high damping, these pressure gradients are developed over small surface areas.
With current manufacturing processes, it is necessary to have relatively large surface areas on the bearing surface for making process control measurements such as optical fly height measurements and slider surface curvature measurements. The small bearing pads may not be sufficiently large to make these measurements accurately or may be in the wrong locations. Additional, larger air bearing pads would then need to be added to the rail surfaces to allow for the process control measurements. However, these large air bearing pads would generate pressure over large surface areas, which would in turn generate a large amount of upward force on the slider. To compensate for this large upward force, a number of the small damping features would need to be removed so that the slider would fly at the correct flying height. By removing the damping features, the air bearing would have a reduction in damping performance.
A slider is therefore desired which has high stiffness and damping performance while providing reference surfaces that can be used for measuring fly height and slider curvature. The present invention addresses these and other problems, and offers other advantages over the prior art.
One embodiment of the present invention relates to a disc head slider which includes a slider body having a disc-facing surface, a recessed area positioned on the disc-facing surface, and a raised rail positioned on the disc-facing surface adjacent the recessed area. The raised rail includes a bearing surface and a recessed step surface which is recessed from the bearing surface and is raised from the recessed area. A plurality of bearing pads are formed on the recessed step surface and have upper surfaces that together define the bearing surface. A non-bearing pad is formed on the recessed step surface, has an upper surface, which is generally coplanar with the bearing surface, and has a pointed leading pad edge.
Another embodiment of the present invention relates to a disc head slider which includes a slider body having a disc-facing surface, a recessed area positioned on the disc-facing surface, and a raised rail positioned on the disc-facing surface adjacent the recessed area. The raised rail includes a bearing surface and a recessed step surface which is recessed from the bearing surface and is raised from the recessed area. A plurality of bearing pads are formed on the recessed step surface and have upper surfaces that together define the bearing surface. A non-bearing pad is formed on the recessed step surface, has an upper surface, which is generally coplanar with the bearing surface, and has a leading pad edge and lateral side edges. A moat is recessed into the recessed step surface and extends along the leading pad edge and the lateral side edges of the non-bearing pad.
Yet another embodiment of the present invention relates to a disc head slider which includes a disc-facing surface, a recessed area positioned on the disc-facing surface, and a first raised rail positioned on the disc-facing surface adjacent the recessed area. The first raised rail includes multiple coplanar bearing surfaces and a non-bearing reference surface which is coplanar with the multiple bearing surfaces and is substantially isolated from air flow along the first raised rail.